The present invention relates to circuits and methods for automatically controlling the frequency of a signal in a system such as a radar in which the frequency must be maintained with a high degree of accuracy.
To date, analog instrumentation, generally featuring variations of a phase-lock-loop (PLL) device, has been used to control frequency drifts in a signal. Although devices based on analog circuitry provide adequate performance, they are often too restrictive to a particular application, and, therefore, offer little or no flexibility when the source signal to be controlled takes on a new frequency band. In a related issue, analog devices are often too costly to implement and difficult to maintain at optimum performance on a long-term basis.
A continuing need exists for improvements in the area of frequency control, particularly in the radar applications in which the primary considerations include flexibility, accuracy and low cost.